Various types of polymeric and co-polymeric coating compositions are used by consumers today, ranging from paints and varnishes for cars, boats and homes to topical applications for skin or nail coatings. In fact some, polymer coatings actually are prepared as sheet material, such as a shower curtain. However, they have in common a need to provide a fluid delivery that dries as a smooth, durable surface, capable of withstanding exposure to sun, light, air, moisture, heat, cold and chemicals present in the environment without becoming brittle and chipping, spalling, cracking, shattering or disintegrating, especially when subjected to external physical stress or movement.
Drying, setting, or curing time and durability are two of the most important characteristics of film coating compounds. As drying time is decreased, durability may be adversely affected. As a result, a balance of resins, plasticizers, polymers, catalysts, curing agents and solvents are selected and used to permit rapid drying and/or curing, but also to maintain the dried film in a dynamic and somewhat flexible state for as long as possible, while at the same time providing a hard, durable, smooth coat that will resist denting and abrasion. The plasticizers typically added to polymeric compositions, often with other components, are used to counteract the effects of aging and to enhance durability and flexibility of the coating. However, plasticizers tend to become volatile at ambient temperatures. Consequently, a substantial amount of plasticizer flashes from the substrate, along with the solvents, as the film dries. Moreover, the remaining plasticizer component continues to volatilize, particularly at the coating/air interface, and molecules are steadily released from the dried coating into the air, soon leaving the coating dry and brittle.
Using nail coating compositions as an example, the polymeric coatings typically contain one or more film formers in combination with other formulation additives, such as solvents, coalescent agents, plasticizers, thickeners, suspension aids, and pigments. Nitrocellulose, is often used in combination with a secondary film former, such as toluene sulfonamide formaldehyde, to improve properties, such as application, wear, and gloss. Nevertheless, although nitrocellulose has excellent pigment wetting capabilities, and forms a film, which dries quickly, has high gloss, good hardness, and good resistance to abrasion and chemicals, it has disadvantages. For example, formulations containing nitrocellulose tend to discolor the nails, and over time tend to drop in viscosity and may lose the ability to form a hard film. Also, for solubility reasons, nitrocellulose is undesirably formulated with organic solvents, such as ethyl acetate, methyl ethyl ketone, and toluene. The organic solvents, however, also tend to discolor the nails, and make them brittle. Therefore, a plasticizer component acts to combat brittleness, but any plasticizer added to the coating must also withstand the drying effect of the solvents.
Other approaches utilize a blend or dispersion of polymers, which will form a film from an aqueous medium, e.g., polyurethane or polyacrylate compositions. However, these polymers tend to have inferior pigment wetting properties, and form films which are not durable, and have poor resistance to chemicals and abrasion. Accordingly, the present invention addresses these problems by incorporating into an aqueous nail coating composition, agents, such as a plasticizing agent, which is continuously released in a controlled manner into the post-application, dried film coating.
To facilitate continuous or controlled release, two major types of micropackaging or microcontainment systems have been developed for packaging and containing active liquids, fluids and solids in the form of free-flowing beads, particles, or powders. In entrapment systems, the active liquid, ingredient, or functional material is contained by sorption within a microscopic polymeric matrix or lattice. The polymer lattice containment results in conversion, for example, of liquids, waxes, or solids into free-flowing particles. By comparison, in microencapsulation, small droplets of the active or functional liquid or solid are coated with a continuous film of polymeric material. The process of microencapsulation and formation of microcapsule systems is further described in the Encyclopedia of Chemical Technology, Vol. 13, J. A. Herbig, “Microencapsulation”, pp. 436-456, John Wiley & Sons, Inc., 2nd edition, 1967, and various United States patents including U.S. Pat. Nos. 2,969,330, 3,137,631, 3,341,466, 3,516,943 and 3,415,758.
Micropackaging by encapsulation or entrapment protects the active liquids or solids from deterioration and exposure to air or even light, and increases longevity. Typical polymer entrapment particles range in particle size from less than 0.10 microns to, for example, 5,000 microns, that is from powders to beads. The characteristics of the entrapment materials may be varied according to the lattice wall co-polymers and the ratio or percentage of co-polymers comprising the particles. Inorganic or organic hollow, spherical polymeric powders, sized under 1000 microns, are often referred to as “microspheres.”
Rohm and Haas Co. developed a Meitzner-Oline portfolio of technologies for producing polymerization processes and products therefrom, including U.S. Pat. Nos. 3,531,463; 4,224,415 and 4,221,871. In general, the patents teach that a resin forms a matrix of solid co-polymer, having a macroreticular structure, which is permeated by small channels or voids into which liquids can penetrate. The resulting co-polymeric ionic resin complex, particularly when cross-linked, is effective for absorbing organic fluids or separating mixtures of organic fluids. The matrix is formed by the suspension co-polymerization of a monovinyl carbocyclic aromatic compound or an ester of acrylic or methacrylic acids, with a polyethylenically unsaturated monomer dissolved in a organic liquid- of mixture of organic liquid-solvent. A high degree of cross-linking of the polymerized monomer results in an enhanced macroreticular structure with many small channels, and also provides enhanced durability. Other patents such as U.S. Pat. No. 6,323,249, as well as the references cited therein, provide additional teaching in the art that may be used for comparative purposes.
The microchannels formed by the Meitzner-Oline process are separate and distinct from the micropores formed in by other cross-linked polymers. During formation of the co-polymer, solubility of the monomer of the co-polymer is decreased as precipitant is added during phase separation of the monomer phase. As a result as the concentration of co-polymer increases and the concentration of monomer decreases, as compared to the co-polymerizing mass. Thus, the precipitant is repelled by the co-polymer and actually squeezed out of the co-polymer phase, leaving the series of microchannels.
U.S. Pat. No. 4,690,825 (Applied Polymer Systems, Inc.) teaches a method for the sustained release delivery of impregnated materials for topical application, including vitamins, steroids, insect repellents, ultraviolet absorbents, hair growth promoters, acne treatments and fragrances, alone or from a carrier or cosmetic solid. The delivery vehicles are polymeric beads formed by a polymerization process in which the active material is the porogen during the pore forming process. As a result, the active material is trapped and held within the substantially non-collapsible pore network. Along with related patents U.S. Pat. Nos. 5,145,675 and 5,955,109, the polymeric controlled release delivery system comprises the materials and methods used in the controlled release delivery of active substances.
Optimally, the active ingredient particles in the Applied Polymer Systems' processes are spherical in shape ranging from about 0.10 to 100 microns in diameter, imparting a smooth feel, prepared by suspension polymerization in a liquid-liquid system. A solution is formed by polymerizing one or more polymers by a free radical suspension polymerization process, and the active ingredient is delivered from the macropores formed therein. However, no delivery is made from the polymerized particles or the micro- or mesopores formed during the polymerization process.
U.S. Pat. No. 4,844,885 (Chernack) teaches a composition containing pressure-sensitive microcapsules, wherein the composition comprises a liquid phase capable of solidification, e.g., as a nail lacquer. Substantially evenly dispersed throughout the liquid phase is a multiplicity of microencapsulated droplets of a solvent phase. The shells of the microcapsule are ruptured under applied pressure for selectively releasing the solvent phase, e.g., nail lacquer remover, for dissolving the liquid phase after it has solidified.
U.S. Pat. No. 5,922,334 (Krasnansky et al.) provides an aqueous nail coating composition comprising: at least one film forming agent comprising a dispersion of multi-phase polymers; wherein the multi-phase polymers comprise at least one inner polymer phase and at least one outer polymer phase; wherein the inner polymer has a Tg of at least 30° C. and comprises as polymerized units at least 2 weight percent of a hydrophobic monomer, based on total weight of monomer in the inner polymer; wherein the outer polymer has a Tg from −15° C. to 35° C., and comprises as polymerized units at least 3 weight percent of a second hydrophobic monomer; wherein the weight ratio of the inner polymer to the outer polymer is from 20:80 to 70:30; and provided that when the outer polymer has a weight average molecular weight equal to or greater than 200,000, the inner polymer further comprises at least 0.01 weight percent cross-linking agent based on total monomer in the inner polymer, and the outer polymer has a soluble fraction in tetrahydrofuran of at least 15 weight percent, and comprises from 3 weight percent to 70 weight percent of the second hydrophobic monomer based on total monomer in the outer polymer.
None of the prior art coating compositions have been able to exhibit durability during wear, which prevents the coating from hardening and becoming more brittle, which invariably results in the cracking and breaking of the film coated surface. In particular, in the nail coating industry, the prior art continues to search for a coating that provides a high gloss, defined color, long wear and chip resistance, and yet retains nail flexibility, durability, resistance to abrasion and chipping, and adherence without brittleness over extended periods of time.